Hard disk drives provide fast non-volatile, rewritable and economical computer memory. Most disk media, such as magnetic hard disks, magneto-optical disks and phase-change optical disks, involve codings by various deposition techniques such as sputtering or chemical deposition. One of the types of sputtering machines for sputter-deposition of a succession of various layers onto the disk surfaces to produce the memory media is an in-line (or “pass-through”) machine. Such a machine includes either a linear arrangement of relatively small, individual but connected chambers, or one or two long chambers with vacuum transition locks at each end of the line. Processing stations are located either along the long chambers or in each individual chamber. During deposition, a multiple-disk substrate carrier, called a pallet, continuously passes in front of the sputtering targets or sources.
In high-speed operations, load robots are employed to transfer disk media from a presentation location to load the disks into a transfer pallet. Using the end-effector, the robot picks a group or series of axially aligned disks from the presentation location, and places the disks one at a time into the pallet.
A previous design of a robotic end-effector used by load robots to transfer disk media employs two opposing mandrels mounted to a central hub. The mandrel is a one-piece cantilever design constructed from “PEEK” plastic, and has thirteen slots for holding disks. In operation, the robot inserts the mandrel into the center of the axially aligned disks at the presentation location, removes them from the presentation location, and subsequently places the disks one at a time into the transfer pallet. There are certain concerns related to the conventional device, caused by the one-piece mandrel design made of plastic. These concerns include quality, throughput and line yield loss.
Scratches and dings in a disk may be caused by inaccurate placement of the disk in the pallet by the robot, affecting the quality of the disk. Dimensional instability of the plastic material of the one-piece mandrel, as well as the flexure of the mandrel, may be a major factor in the accuracy of the placement of disks into the pallet. Another quality factor is the ability to track the disk products through the factory. For example, a product may be tracked in lots of twenty-five disks. Using a mandrel having a different number of slots than the disk lot size causes the lots to be broken up and disordered during a transfer process. This makes product tracking more difficult and prone to errors.
Another concern with conventional design relates to the throughput. Using a thirteen-slot mandrel design, the robot may frequently run out of disks while loading a pallet. The robot must then take time out from the loading to resupply itself with disks, causing a reduction in throughput. Another throughput factor is the relatively limited payload that can be carried by the one-piece plastic design, due to the flexure of the plastic mandrel under load. As such, the plastic design of the mandrel may not work well with next generation media form-factors, which are expected to be heavier. Another throughput issue is that periodic maintenance is difficult and time consuming, causing lost production while a technician replaces and recalibrates the one-piece plastic mandrels.
A still further concern regards line yield loss. Over time, placement accuracy of a disk into the pallet can degrade to the point where disks are misloaded in the pallet. The degrading of the placement accuracy may be due to the one-piece plastic design of the mandrel. The disks will either fall out onto the ground, or fall back into the mandrel and have to be removed. In either event, the disks become scrap. Further, in the event of a severe misload of a disk into the pallet, the disk can get lodged such that the robot rips the disk out of the pallet, resulting in damage to the pallet, the mandrel, and any previously placed disks. Also, error recovery from misloads has a significant impact on line yield loss.